The disclosure of Japanese Patent Application No. 2000-381463 filed on Dec. 15, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention generally relates to a brake control system of a vehicle such as an automobile. More particularly, the invention relates to a brake control system that controls a braking force to the vehicle based on an operational force applied to a braking member by a vehicle operator, and a displacement amount of the braking member applied by the vehicle operator.
2. Description of Related Art
There has been a well-known braking controller in which a braking control amount is set based on a depression force of a brake pedal applied by a vehicle operator and a stroke of the brake pedal resulting from being depressed by the vehicle operator. This technology is disclosed in JP-A-11-504296.
In the aforementioned braking controller, at least one of a plurality of depression force sensors for detecting the depression force applied to the brake pedal, and a plurality of stroke sensors for detecting a stroke of the brake pedal, are provided. Based on the resultant values detected by those sensors, the amount of the braking operation applied by the vehicle operator is estimated. Accordingly, this makes it possible to estimate the amount of the braking operation applied by the vehicle operator.
In a vehicle braking controller that has a cutoff device that cuts off a passage between a master cylinder and wheel cylinders corresponding to the respective wheels, and a high-pressure fluid supply source that supplies a high-pressure hydraulic fluid to the passage, high pressure hydraulic fluid is supplied to the master cylinder from the high-pressure fluid supply source to force back the brake pedal when an abnormality occurs in the cutoff device and the cutoff device is not placed in an open state sufficiently. As a result, the stroke of the brake pedal is reduced even if the respective sensors are in normal operating states.
When a combination of a single depression-force sensor and two stroke sensors is employed, the amount of the braking operation applied by the vehicle operator is estimated mainly on the basis of the detection values of the two stroke sensors which have precedent over the detection value of the single depression-force sensor. In the aforementioned case, the estimated amount of the braking operation may be smaller than the braking amount required by the operator. This problem may also occur when the amount of the braking operation applied by the operator is estimated on the basis of the detection values of two depression-force sensors and two stroke sensors.
It is an object of the invention to provide a brake control system and method that controls the braking force applied to each wheel in accordance with the braking operation of a vehicle operator by more optimally estimating a braking amount required by the operator.
The aforementioned brake control system and method includes a cutoff device that cuts off a passage between a master cylinder and a wheel cylinder provided for each wheel of the vehicle, a high-pressure fluid supply source that supplies a high-pressure operating fluid to the passage between the cutoff device and the wheel cylinder, at least two operation force detectors that detect a force applied by an operator of the vehicle so as to operate a braking member, at least one displacement detector that detects a displacement of the braking member operated by the operator of the vehicle, and a hydraulic pressure controller that controls a hydraulic pressure within the wheel cylinder on the basis of values detected by the at least two operation force detectors and the at least one displacement detector. In the braking controller according this invention, the number of the operation force detectors is larger than the number of the displacement detector(s). When there is inconsistency among the values detected by the at least two operation force detectors, and the at least one displacement detector, the hydraulic pressure within the wheel cylinder is controlled on the basis of less than all of the detected values.
In the aforementioned brake control system and method, the number of the operation force detectors is larger than the value of the displacement detector(s), and the hydraulic pressure controller controls the hydraulic pressure in the wheel cylinder on the basis of the detection values in which there is consistency. Therefore, the braking amount required by the vehicle operator may be estimated on the basis of the detection values in which there is consistency without using the detection values in which there is inconsistency. As a result, the braking force applied to each wheel may be more optimally controlled in accordance with the amount of braking required by the vehicle operator.
In the brake control system and method in accordance with an embodiment of this invention, the at least one operation force detector includes two operation force detectors and the at least one displacement detector includes one displacement detector. When there is consistency between values detected by the two operation force detectors, and there is inconsistency between the values detected by the two operation force detectors and a value detected by the one displacement detector, the hydraulic pressure controller controls the hydraulic pressure within the wheel cylinder on the basis of the values detected by the two operation force detectors.
When there is consistency between values detected by the two operation force detectors, and there is inconsistency between the values detected by the two operation force detectors and the value detected by the displacement detector, the hydraulic pressure in the wheel cylinder is controlled on the basis of the values detected by the two operation force detectors. Even if an abnormality occurs in the cutoff device which may cause the high-pressure hydraulic fluid to flow from the high-pressure fluid supply source to the master cylinder via the cutoff device, and the braking member like a brake pedal is forced back to reduce the displacement degree, the hydraulic pressure within the wheel cylinder is controlled on the basis of the values detected by the two operation force detectors. Accordingly, the detection values that do not accurately reflect the braking amount required by the vehicle operator can be ignored. As a result, the braking amount applied to each wheel can be controlled so as not to be lower than the braking amount required by the operator.
In the brake control system and method in accordance with an embodiment of this invention, the at least one operation force detector includes two operation force detectors and the at least one displacement detector includes one displacement detector. When there is inconsistency between values detected by the two operation force detectors, and there is consistency between one of the values detected by the two operation force detectors and a value detected by the one displacement detector, the hydraulic pressure controller controls the hydraulic pressure within the wheel cylinder on the basis of the one of the values detected by the two operation force detectors and the value detected by the one displacement detector.
When there is inconsistency between values of the two operation force detectors, and there is consistency between one of the values of the two operation force detectors and the value detected by the displacement detector, the hydraulic pressure within the wheel cylinder is controlled on the basis of the value detected by one of the operation force detectors and the value detected by the displacement detector. Accordingly, the braking amount required by the operator may be estimated on the basis of the values in which there is consistency without using those values in which there is inconsistency, thus controlling the braking force applied to the wheel optimally in accordance with the braking amount required by the operator.
In the brake control system and method in accordance with an embodiment of this invention, the hydraulic pressure controller determines whether each pair of the detected values has consistency by determining whether a relationship between the each pair of the detected values is within a predetermined normal zone.
In the brake control system and method in accordance with an embodiment of this invention, the operation force detector detects a pressure within the master cylinder.
In the brake control system and method in accordance with an embodiment of this invention, the displacement detector detects a stroke of the braking member.
In the brake control system and method in accordance with an embodiment of this invention, when there is consistency between the values detected by the two operation force detectors, and there is inconsistency between the values detected by the two operation force detectors and the value detected by the one displacement detector, the hydraulic pressure controller controls the hydraulic pressure within the wheel cylinder on the basis of an average value of the values detected by the two operation force detectors.
In the brake control system and method in accordance with an embodiment of this invention, when there is consistency among the values detected by the at least one operation force detector and the at least one displacement detector, the hydraulic pressure controller controls the hydraulic pressure within the wheel cylinder on the basis of an average value of the two detection values of the two operation force detectors, and the detection value of the displacement detector.
In the brake control system and method in accordance with an embodiment of this invention, the hydraulic pressure controller determines that there is consistency in a relationship between values detected by the two operation force detectors when the two detection values are substantially the same.
In the brake control system and method in accordance with an embodiment of this invention, the hydraulic pressure controller determines whether each pair of the detected values has consistency by determining whether a relationship between the each pair of the detected values is within a predetermined normal zone. When a relationship between the values detected by the two operation force detectors is within the normal zone, and relationships between the values detected by the two operation force detectors and the value detected by the one displacement detector are within the same abnormal zone that deviates from a predetermined normal zone with respect to the relationship between the values detected by the two operation force detectors and the one displacement detector, the hydraulic controller controls the hydraulic pressure within the wheel cylinder on the basis of the values detected by the two operation force detectors.
In the brake control system and method in accordance with an embodiment of this invention, the hydraulic pressure controller determines whether each pair of the detected values has consistency by determining whether a relationship between the each pair of the detected values is within a predetermined normal zone. When a relationship between the values detected by the two operation force detectors is within the normal zone, and relationships between the values detected by the two operation force detectors and the value detected by the one displacement detector are within different abnormal zones that deviate from a predetermined normal zone with respect to the relationship between the values detected by the two operation force detectors and the one displacement detector, the hydraulic controller places the cutoff device in an open state such that the hydraulic pressure within the wheel cylinder is directly controlled by the hydraulic pressure within the master cylinder.
In the brake control system and method in accordance with an embodiment of this invention, the hydraulic pressure controller determines whether each pair of the detected values has consistency by determining whether a relationship between the each pair of the detected values is within a predetermined normal zone. When a relationship between the values detected by the two operation force detectors is not within the normal zone, and relationships between the values detected by the two operation force detectors and the value detected by the one displacement detector are within different abnormal zones that deviate from the normal zone with respect to the relationship between the values detected by the two operation force detectors and the one displacement detector, the hydraulic controller places the cutoff device in an open state such that the hydraulic pressure within the wheel cylinder is directly controlled by the hydraulic pressure within the master cylinder.